95 175 intruder will not keep fuel pressure

Hello, i have a friend with a 175 intruder that has been having problems with his motor for 2 years now and nobody seems to be able to diagnose it. So i figured i would give this a shot and hope that it works out. Sorry if this gets lengthy:
The fuel ball will not stay pumped up at idle. Everytime he stops and turns the motor off it is like the fuel just drains back into the tank. You have to go pump up the ball even if the boat just sat for 10 minutes. Then once it starts you have to periodically go back and pump up the ball agian or it will die. Once he takes off, it is fine. If he is running wide open and brings it back down to idle it is fine. Here is the list of what has been tried:

1. Replaced fuel lines and primer bulb a few times (jsut because we kept being told this)
2. Replaced fuel pump
3.Replace check valve in boat tank
4. Bypassed selector switch in boat for aux tank
5. Replaced powerpack (longshot, i know)
6. Installed a different set of carbs completely off another motor
7. Ran motor on aux 6 gallon plastic tank
8. Switched motors off another boat. His motor ran fine on the other boat, but the replacement motor did the exact same thing on his boat

We are stumped now after the whole motor switching episode, it has to be in the boat somewhere, but what is left???? By the way, boat is a 03 Alumacraft Trophy 190.

Thanks for any help
Steve

What inch I.D. hose you put back on it? With you putting the other motor on it and it doing the SAME THING, IT HAS TO BE FROM THE HOOKUP TO THE TANK.... SOMEWHERE... Does the boat have dual tanks?

we put 3/8 lines from the tank to the motor. The boat does have a main and aux tank (aux tank inside main tank) with a selector switch. We completely bypassed that selector switch to rule that out and hooked the fuel line up directly to both the main fuel tank lines and then to the aux fuel tank lines with no change.

It seems like one of the things we have tried would at least narrow down our search. So far about the only thing we have concluded also is that it has to be the boat somewhere......

Thats a tough one, maybe one of the real gurus will step in............

This is a long shot but.... I watched a tech pull his hair out trying to find it.


The fitting that the oil and fuel lines are hooked to where they enter the motor cover is plastic, the Tech found if he removed this fitting and blocked one end of the fuel barb and pulled a vacuum on the other end it would leak air but did not leak fuel... http://www.bassboatcentral.com/smileys/doh.gif

This took a while to find and I, nor He will ever forget it.

A couple of other thoughts, has he removed the flame arrester fitting for the air side of the OMS pump, if the hole it screws into is blocked with debris it could cause this.

Are the carbs wet with fuel? Carb bowls warped?

Has he checked the compression?

Vapor separator tank and vapor pump?

Thanks for the idea's guys, i knew you guys would have something. The oms pump was replaced. The carbs have fuel in the bowls, just nothing in the lines from what he is telling me and we didn't check the carb bowls for warpage yet. The compression readings are good and i will check the fitting that you were talking about.
I know the one thing that he hasn't checked yet that we were wondering if it could be something was the pickup line inside the tank. Would a small leak in that hose do this? The anti syphon check valve that he changed was a little elbow fitting on the top of the tank, is there another one inside the tank anywhere?
Thanks for the replys and keep any other ideas coming, because this has been two years with this problem on an otherwise great boat.
Steve

He could get a clear hose and attach it at the fuel pick up on the tank, start the motor, with water of course and look for air bubbles in the clear line, if none there move the hose to the outlet side of the next part in the fuel system, switching valve, no bubbles, move it to the other side of the primer bulb, no bubbles, move it to the fuel filter, this will check the fitting I posted about.


Just because all these parts have been changed or removed from the system does not mean that they could not be part of the problem.

hmm, never really thought of the clear hose deal. Guess sometimes you look so hard at something that you over-complicate it and forget to go through all of the steps to trouble shoot. I'll give that a shot first part of next week. Thanks,
Steve

I agree with Rusty! If you changed out the motors and fuel lines (W/new primer bulb) from fuel tank pick-up to motor. And had the same results, I'd change out the fuel tank pick-up ay. also make sure the fuel tank vent is clear (damn mud daubers will drive a tech to drink excessively.)
Oetiker clamps on all fuel lines, from the fuel pick-up to the oms pump, their expensive, but they do make a difference.